A satellite in low earth orbit (usually considered between 200 km to 1000 km above the earth's surface) encounters a plasma environment having low background pressures and high electron and ion densities. The background pressures can be about 10.sup.-7 torr while the electron and ion densities may be about 10.sup.5 /cm.sup.3. Standard bushings and insulators have proved unsuitable for use in such an environment when the voltage is above a few hundred volts. In such a low background pressure, the insulator outgasses and desorbs adsorbed or absorbed gasses. This results in higher local pressure near the insulator. These gasses ionize and ions impinge on the insulator surface causing secondary electron emission. Above a few hundred volts, these conditions result in flashovers on the insulator surface.
A very high voltage (up to one million volts) bushing has been proposed for bringing a conductor into a vacuum vessel. This bushing includes an inner tube of a resistive material receiving the conductor. A stack formed by alternating annular glass members and aluminum rings surrounds the tube with rings engaging the tube. A field shaping ring is held by each aluminum ring to partially cover adjacent glass members. In order to fit the tube inside of the aluminum rings, the tube is contracted by cooling or vacuum and, after insertion into the rings, is allowed to expand. For further information concerning the structure and operation of such a bushing, reference may be made to U.S. Pat. No. 3,126,439.